Similar problem to how you pronounce the University of Notre Dame. Do you go 'merican and call it Noter Dame or go No-tra Dawm (lol at my phonetic spelling) like the Frenchies and their cathedral. Pronouncing things in their native accident is IMO taking things too far, try saying the Dutch beer "Grolsch" in it's proper guttural glory.

Correct. And it would be perfectly fine if you are speaking German and pronounce it as such. To spell it out as pheonetically as possible in English, it's pronounced POGH-sheh, with a throaty gutteral sound replacing the "r."

But when someone's speaking English, they sound retarded pronouncing Porsche as if they're speaking German, especially when they don't apply the same rule to other makes (not to mention reverting back to the English pronouciation of "Carrera", too). How many people do you encounter who pronounce Mazda as MAT-su-DA while speaking English?

This is true. But when speaking English, do you pronounce quesadilla as "kay-suh-DILL-uh"? Or does it sound retarded when someone says "keh-sah-DEE-ya"

What about when people pronounce Audi like "AH-dee"? Do they sound retarded when they say "OUW-dee"? etc.

I say "I drive a BM"...as in Bee-Em. I guess, Americans don't really understand what 'BM' really is. When I tell my friends that, they say "what?". I know 'BM' is understood as BMW in many places outside of the US